You can go even a step further and introduce a second filter based on age in order to re-transform the foam into beer again.

Only thing for a final version I would do is adding more randomisation of the beer emitter so that the stepping is no longer visible, and maybe the difference in density between beer and foam does not need to be so much different from each other so that the foam is rising more slowly to the top.

Thanks to both of you for your comment. Here is the last version of my test : https://youtu.be/PnhsU_VTHBoChristian I took care of the randomization of the pouring and gave a little bit more resolution. Now Foam is transform to beer again at the end.Next step is adding bubble when pouring, and gaz after pouring.